Multi-Function Peripherals (MFPs) having a decoloring function are known. Decoloring indicates removing a color of an image that has been printed with decolorable toner. The MFP removes the color of the image by heating the sheet bearing the decolorable toner.
The MFP typically includes a cassette for new sheets and a cassette for decolored sheets. The MFP sometimes forms images on the decolored sheets.
A post-processing apparatus aligns sheets on a processing tray and performs a post-processing such as a stapling process or a sorting process. The post-processing apparatus discharges a bundle of the sheets to a discharge tray.
However, in the post-processing apparatus, a deficiency sometimes occurs in conveyance of a decolored sheet. If a sheet is decolored, the sheet often loses its stiffness and may easily curl. Such deformation can cause a jam or alignment failure in the post-processing apparatus.